\section{Challenges}
When it comes to the realization of the Internet of Things, several challenges can be identified.
\subsection{Multi-Protocol Integration}
A key challenge for the realization of the Internet of Things is the integration of a variety of protocols that are used for the automation of devices. Wireless protocols like Zigbee or ZWave require devices that act as protocol gateway to interact with each other. Furthermore, several protocols used for interaction with sensor and actuator devices do not use or do not support IP as transport. 

\subsection{System Architecture}
A communication architecture needs to be created that supports the massive number of communication partners and provides the facilities to describe and discover the services offered by devices. A creation of a service-oriented architecture is a reasonable idea for such a large-scale system.
\begin{figure}[h]
	\centering
		\includegraphics[width=0.75\columnwidth]{res/iot_soa_architecture}
	\caption{System Architecture\cite{atzori2010internet}}
	\label{fig:architecture}
\end{figure}

Figure~\ref{fig:architecture} outlines the communication layers that are required, starting at the level of devices that are finally made available and controlled by applications.

\subsection{Semantic integration}
The semantics of different information models used by protocols and standards need to be integrated. Cross-domain ontologies or semantic web technologies may help to solve these issues.

\subsection{Trust, Privacy and Security}
Making appliances used in private life available on the Internet may enable abuse and malicious interactions. Exposing remote control capabilities over these devices might threaten security. Furthermore, the total observation of all aspects of a person's life creates privacy concerns that need to be addressed by communication infrastructure designers.

\subsection{Scalability}
Providing applications and services for the Internet of Things, a network of potentially billions of devices, requires special considerations regarding scalability in the conceptual and design phase. 
